Liquid metal could allow 3D printing of custom circuit boards

Researchers at the North Carolina State University are onto a 3D printing process that lets you create objects with drops of liquid metal. Nope, these aren't hot, molten balls of metal; instead, the researchers created a liquid metal alloy that simply clumps together like drops of oil even at room temperature.

The metal alloy, comprised of 75 percent gallium with 25 percent indium, comes out of a syringe-headed 3D printer. The printer creates objects by stacking small liquid metal droplets – which can be as small as 10 microns across – on top of each other.

The drops stick to one another on contact, but still retain their shape so they won't merge into a single, larger droplet. It can do this because when the liquid metal is exposed to air, the alloy develops an oxidized skin that lets it hold its shape.

The final objects themselves look like a slightly melted array of Buckyball magnets that got mixed up with a game of World of Goo. Michael Dickey, an assistant professor of chemical and biomolecular engineering at NC State and co-author of the paper, told us that you can't pick up the objects because it would be like trying to pick up a drop of water.

A prototype device composed of two LEDs connected by a stretchable wire bond and embedded in PDMS.

In addition to creating cool-looking liquid metal structures, the printer can also extrude liquid metal wires to create flexible and stretchable electronics--the syringe needle simply creates a blob that adheres to a substrate. From there, the needle continues to extrude a long line of material into a metal wire that can be several centimeters long. These liquid metal wires can conduct electricity, making them perfect for custom circuit boards.

Michael also explained that these metal wires could be embedded into materials to create any number of stretchable components. This could include everything from antennas, flexible displays, to simple stretchable electronics such as a flexible LED array.

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